Скачать или смотреть How to Replace $1 with the Matched Group in Java using RegExp

Learn how to replace `$1` with the matched group in Java using regular expressions in your code. A step-by-step guide for Java developers.
---
How to Replace $1 with the Matched Group in Java using RegExp

Manipulating strings using regular expressions (RegExp) is a powerful tool in Java, particularly useful for search, validation, and replace operations. A common operation involves replacing matched groups in a string. This guide will explore how to replace $1 with the matched group in Java using regular expressions.

Understanding Matched Groups

In Java's regular expression syntax, parentheses () are used to create groups within patterns. Each group can then be accessed using a dollar sign $ followed by the group number. For example, $1 refers to the first capturing group.

Example Scenario

Let's assume we have a string and we want to replace parts of it by referencing a matched group.

Initial String

[[See Video to Reveal this Text or Code Snippet]]

Regular Expression Pattern

Let's define a pattern that matches the format Name: Number:

[[See Video to Reveal this Text or Code Snippet]]

Replacement String

We want to switch the places of the name and the number, separated by a hyphen -:

[[See Video to Reveal this Text or Code Snippet]]

Replacement Operation

Using the replaceAll method from the String class, we can perform the replacement:

[[See Video to Reveal this Text or Code Snippet]]

Explanation

Pattern: (\w+ \w+): (\d+)

\w+ \w+: Matches one or more word characters followed by a space and then one or more word characters (captures the name).

:: Matches a colon.

(\d+): Matches one or more digits (captures the number).

Replacement: $2 - $1

$2: Refers to the second matched group (the number).

-: Adds a hyphen between the groups.

$1: Refers to the first matched group (the name).

Full Java Code

Here is the complete code for the example:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By understanding how to use matched groups and the $ notation, you can leverage Java's regular expressions to manipulate and reformat strings efficiently. This approach is very helpful in various scenarios, such as data validation, data transformation, and text processing.

Whether you're just starting with Java or looking to refine your skills, mastering RegExp replacements will significantly enhance your coding toolkit.